WASHINGTON (CNNMoney.com) -- More criminal indictments will come down the pike as corporate America struggles with the ever-growing stock options backdating scandal, according to an assistant director at the FBI.

In an interview Thursday, Chip Burrus, an assistant director of the Federal Bureau of Investigation, said the bureau is vigorously investigating the stock options practices of 55 corporations and sees more indictments coming as the agency works to prove knowledgeable wrongdoing on the part of corporate executives.

It's hardly an easy task. For one thing, backdating stock options isn't necessarily against the law if corporations provide the proper disclosures. At issue is whether companies adjusted dates on options grants to ensure great profits for executives and didn't disclose those activities, misleading the investment community. And proving actual intent to defraud investors is a challenge.

At last count, about 120 companies either are under scrutiny by the government or have launched internal investigations into their options practices. But to date, only Brocade Communications (up $0.15 to $8.66, Charts) and Comverse Technologies have actually received criminal indictments against their top executives.

Still, in recent days, more corporations have ousted or accepted the resignation of a number of high-level executives in relation to the stock options scandal. In the past week alone, former CNET (up $0.05 to $9.19, Charts) CEO Shelby Bonnie resigned, while former McAfee (up $1.30 to $27.94, Charts) CEO George Samenuk retired, in part owing to the stock options backdating probes.

And Monster Worldwide Inc.'s (down $0.19 to $39.55, Charts) CEO Andrew McKelvey, who was a 39-year veteran with the company, stepped down from his post as a result of the investigations into the company's stock options practices.

"Backdating stock options is basically betting on a horse race that's already been run," Burrus said. "It's harmful to the company and does not create a level playing field for investors."

Burrus said while it's too early to tell whether the rash of recent resignations by high-level executives will precede a round of indictments, the FBI is committed to investigating backdated options and bringing forward those cases to the Department of Justice that show, beyond reasonable doubt, that executives willfully pocketed millions and deceived investors.

"I do see more indictments coming," he said.

But Burrus said the stock options scandal is unlikely to result in the same type of fervor as the previous Enron and WorldCom scandals. For instance, corporations aren't likely to disintegrate, although there is increasing chatter on Wall Street that McAfee may find itself on the auction block with the departure of its CEO.

Growing hedge fund focus

While options backdating has certainly garnered attention in recent months, Burrus said the hedge fund industry is also a growth area on the FBI's radar screen.

According to the FBI, more than 90 hedge funds have been investigated in the past couple of years. Burrus said the agency is concerned over the fast-paced growth and lack of regulation within the $1.2 trillion hedge fund industry and considers the industry to be a growing threat for average investors as more and more pension funds have started investing in the riskier market.

"Hedge funds are the wild, wild west of investing," he said. "The problem comes when hedge funds become more and more like Ponzi schemes."

He said average investors in pension funds may not know where their money is going. And given the lack of regulation and the generally secretive nature of the hedge fund industry, it's difficult for average investors to hash out when a hedge fund is defrauding them. Case in point: Bayou Management, which collapsed earlier this year as evidence emerged that the founder of the hedge fund lied to investors about its stellar returns.

For that reason, Burrus said the FBI would continue to investigate the hedge fund industry.

No shift away from white-collar crime

The FBI's increased focus on options backdating and the hedge fund industry belies criticism from some legal experts who said, post-Enron, the government is now shifting focus away from white-collar crime, in favor of homeland security matters.

Indeed, white-collar criminal prosecutions have fallen about 29 percent in the past five years, according to an analysis by the Transactional Records Access Clearinghouse at Syracuse University. And the number of FBI agents assigned to investigate financial crimes is also down.

Burrus said before Sept. 11, the FBI had about 2,100 agents focused on white-collar crime. Since then, more resources have been diverted to counterterrorism, leaving about 1,800 agents to investigate financial crimes.

But the number of corporate fraud and securities fraud cases under investigation has actually climbed since last year.

As of Sept. 21, the FBI is investigating 486 corporate fraud cases, up from 423 in the fiscal year 2005. And securities fraud investigations have climbed to 1,160 from 1,139 last year.

Burrus said prosecutions may be down, but that's because the FBI has had to refocus where it spend its resources. Before the Sept. 11 attacks, the FBI would be willing to look into smaller bank fraud and corporate fraud cases that were less complex - some that involved frauds as small as $100,000.

But now the FBI is more selective in the quality of cases it accepts for investigation, choosing more complex cases that require larger resources than local law enforcement has.

Still, Burrus said the FBI would look into smaller-scale frauds - such as those perpetrated during Hurricane Katrina when individuals sought to defraud organizations like the Red Cross - where the impact on the community was significant.

"The focus hasn't shifted away from white-collar crime," Burrus said. "The public can rest assured."